tune2fs

Overview

tune2fs adjusts tunable parameters on ext2/ext3/ext4 filesystems: labels, UUID, mount-count checks, reserved blocks, feature flags, and more. Inspect with tune2fs -l before changing anything.

Syntax

sudo tune2fs [options] device

Common Options

Option	Description
-l	List current superblock contents
-L label	Set volume label
-U UUID\|random\|time	Set UUID
-c max-mount-counts	Max mounts between fsck (-1 disables)
-i interval	Max time between fsck
-m percent	Reserved blocks % for root
-r blocks	Reserved block count
-o mount-options	Default mount options
-O features	Set/clear features (careful)

Safety

• Wrong device ruins the wrong filesystem — confirm with blkid / lsblk -f.
  
• Feature flag changes (-O) can make a volume unmountable on older kernels.
  
• Reserved block percentage affects usable free space for non-root users.

Examples with Explanations

Inspect

sudo tune2fs -l /dev/vg0/root | egrep -i 'label|uuid|block count|reserved|mount count|check'

Label and UUID

sudo tune2fs -L ROOT /dev/vg0/root
sudo tune2fs -U random /dev/sdb1
sudo blkid /dev/sdb1
# update fstab if UUID changed!

Reserved space (big data disks)

sudo tune2fs -m 1 /dev/vg0/data     # 1% reserved instead of default ~5%

Disable frequent forced fsck by mount count

sudo tune2fs -c -1 /dev/vg0/data
sudo tune2fs -i 0 /dev/vg0/data

Still run intentional checks after crashes.

Related Commands

• blkid / e2label — labels/UUIDs
  
• resize2fs — size changes
  
• e2fsck / fsck — checks
  
• dumpe2fs — alternate dump

Additional Resources

• man tune2fs